Posted 30 August 2009 - 10:15 PM

The Louisiana Geological Survey has released the Amite Geologic Quadrangle map authored by Richard McCulloh, Paul Heinrich and John Snead. Its scale is 1:100,000and the map is 28 X 48". It is a multicolored map which describes and illustrates the surficial geology of the Amite Quadrangle. Except for the Mississippi River Delta, this map completes the 30 by 60 degree geologic map coverage of the coast-wise portion of the Louisiana coastal plain underlain by Pleistocene and Holocene sediments. More detail at:

In time, the shapefiles of these maps, as they are proofed and the metadata is compiled, will become available for downloading from a future web page.

While preparing the above maps, it was found that the terraces mapped by Harold N. Fisk for the Williana and Bentley formations in the Rapides, LaSalle, and adjacent parishes are completely imaginary; the Williana Formation, in addition to its terrace, is a nonexistent stratigraphic unit; and there is a lack of any evidence for either the existence of or the contact between the coast-wise portions of either the Bentley and Montgomery formations as mapped by him, Holland, and associated researchers within Southwest Louisiana. The Lissie (Early Pleistocene) and Willis (Pliocene)formations have been reinstated within Southwest Louisiana.

One major problem was at the time that they did their geologic mapping, they had only planimetric maps to use in their geologic mapping and barometric altimimeters, often strapped to a car, as a source of elevation data for delineating extremely low relief (very, very flat) and very gently gulfward dipping geomorphic surfaces. A number of the terrace scarps that they mapped within Southwest Louisiana have been found to be coast-wise fault-line scarp trends.

The 2008 version of the "Generalized Geologic Map of Louisiana" can be found on the above web page or directly downloaded from: